CHELYABINSK, Russia (Reuters) - More than 500 people were injured when a meteorite shot across the sky and exploded over central Russia on Friday, sending fireballs crashing to Earth, shattering windows and damaging buildings.

People heading to work in Chelyabinsk heard what sounded like an explosion, saw a bright light and then felt a shockwave according to a Reuters correspondent in the industrial city 1,500 km (950 miles) east of Moscow.

A fireball blazed across the horizon, leaving a long white trail in its wake which could be seen as far as 200 km (125 miles) away in Yekaterinburg. Car alarms went off, windows shattered and mobile phone networks were interrupted.

"I was driving to work, it was quite dark, but it suddenly became as bright as if it was day," said Viktor Prokofiev, 36, a resident of Yekaterinburg in the Urals Mountains.

"I felt like I was blinded by headlights," he said.

No fatalities were reported but President Vladimir Putin, who was due to host Finance Ministry officials from the Group of 20 nations in Moscow, and Prime Minister Dmitry Medvedev were informed.

A local ministry official said such incidents were extremely rare and Friday's events might have been linked to an asteroid the size of an Olympic swimming pool due to pass Earth at a distance of 27,520 km (17,100 miles) but this was not confirmed.

Russia's space agency Roscosmos said the meteorite was travelling at a speed of 30 km (19 miles) per second and that such events were hard to predict. The Interior Ministry said the meteorite explosion had caused a sonic boom.

Russia's Emergencies Ministry said 514 people had sought medical help, mainly for light injuries caused by flying glass, and that 112 of those were kept in hospital. Search groups were set up to look for the remains of the meteorite.

"There have never been any cases of meteorites breaking up at such a low level over Russia before," said Yuri Burenko, head of the Chelyabinsk branch of the Emergencies Ministry.

WINDOWS BREAK, FRAMES BUCKLE

Windows were shattered on Chelyabinsk's central Lenin Street and some of the frames of shop fronts buckled.

A loud noise, resembling an explosion, rang out at around 9.20 a.m. (0520 GMT). The shockwave could be felt in apartment buildings in the industrial city's centre.

"I was standing at a bus stop, seeing off my girlfriend," said Andrei, a local resident who did not give his second name. "Then there was a flash and I saw a trail of smoke across the sky and felt a shockwave that smashed windows."

A wall was damaged at the Chelyabinsk Zinc Plant (CHZNq.L) (CHZN.MM) but a spokeswoman said there was no environmental threat.

Although such events are rare, a meteorite is thought to have devastated an area of more than 2,000 sq km (1,250 miles) in Siberia in 1908, smashing windows as far as 200 km (125 miles) from the point of impact.

The Emergencies Ministry described Friday's events as a "meteor shower in the form of fireballs" and said background radiation levels were normal. It urged residents not to panic.

Chelyabinsk city authorities urged people to stay indoors unless they needed to pick up their children from schools and kindergartens. They said what sounded like a blast had been heard at an altitude of 10,000 metres (32,800 feet).

The U.S. space agency NASA has said an asteroid known as 2012 DA14, about 46 metres in diameter, would have an encounter with Earth closer than any asteroid since scientists began routinely monitoring them about 15 years ago.

Television, weather and communications satellites fly about 500 miles (800 km) higher. The moon is 14 times farther away. (Additional reporting by Natalia Shurmina in Yekaterinburg and Gabriela Baczynska in Moscow, Writing by Alexei Anishchuk and Timothy Heritage, Editing by Michael Holden)